Systems and methods for providing power supply to current controllers associated with LED lighting

ABSTRACT

System and method for controlling one or more light emitting diodes. For example, the system includes: a power supply controller configured to receive a cathode voltage from a cathode of a diode, the diode including an anode configured to receive a rectified voltage generated by a rectifying bridge, the power supply controller being further configured to generate a first signal based at least in part on the cathode voltage; and a driver configured to receive the first signal and generate a second signal based at least in part on the first signal, the driver being further configured to output the second signal to a gate terminal of a transistor, the transistor including a source terminal coupled to the driver and a first resistor, the transistor further including a drain terminal coupled to the one or more light emitting diodes and an output capacitor connected to the cathode of the diode.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201911316902.5, filed Dec. 19, 2019, incorporated by reference hereinfor all purposes.

BACKGROUND OF THE INVENTION

Certain embodiments of the present invention are directed to circuits.More particularly, some embodiments of the invention provide systems andmethods for providing power supply to current controllers. Merely by wayof example, some embodiments of the invention have been applied to lightemitting diodes (LEDs). But it would be recognized that the inventionhas a much broader range of applicability.

With development in the light-emitting diode (LED) lighting market, manyLED manufacturers have placed LED lighting products at an importantposition in market development. The light-emitting diodes are oftenregulated by a linear constant current circuit of a constant currentcontroller chip. The constant current controller chip usually receives,as an input voltage, a rectified voltage (e.g., VIN) that is generatedby a rectifier. When the rectified voltage (e.g., VIN) reaches itsvalley in magnitude, the input voltage of the constant currentcontroller chip often falls below a threshold voltage, causing thecontroller chip not to operate normally.

Additionally, the LED lighting products often need dimmer technology toprovide consumers with a unique visual experience. Since Triode forAlternating Current (TRIAC) dimmers have been widely used inconventional lighting systems such as incandescent lighting systems, theTRIAC dimmers are also increasingly being used in LED lighting systems.Usually, a TRIAC dimmer clips part of a waveform for the AC inputvoltage during a dimming off period. During the dimming off period, therectified voltage (e.g., VIN) often is pulled down in magnitude by ableeder unit that generates a bleeder current for the TRIAC dimmer, suchthat the input voltage of the constant current controller chip usuallyfalls below the threshold voltage, causing the controller chip not tooperate normally.

To solve these technical problems, the conventional technology oftenemploys an external capacitor, which is used as a power supply to theconstant current controller chip when the input voltage falls below thethreshold voltage. The external capacitor, however, usually increasesthe cost of bill of materials (BOM) for the LED lighting system.

Hence it is highly desirable to improve the techniques related to LEDlighting systems.

BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the present invention are directed to circuits.More particularly, some embodiments of the invention provide systems andmethods for providing power supply to current controllers. Merely by wayof example, some embodiments of the invention have been applied to lightemitting diodes (LEDs). But it would be recognized that the inventionhas a much broader range of applicability.

According to certain embodiments, a system for controlling one or morelight emitting diodes includes: a power supply controller configured toreceive a cathode voltage from a cathode of a diode, the diode includingan anode configured to receive a rectified voltage generated by arectifying bridge, the power supply controller being further configuredto generate a first signal based at least in part on the cathodevoltage; and a driver configured to receive the first signal andgenerate a second signal based at least in part on the first signal, thedriver being further configured to output the second signal to a gateterminal of a transistor, the transistor including a source terminalcoupled to the driver and a first resistor, the transistor furtherincluding a drain terminal coupled to the one or more light emittingdiodes and an output capacitor connected to the cathode of the diode;wherein the power supply controller and the driver are furtherconfigured to: if the cathode voltage has not remained higher than apredetermined voltage threshold for a time duration that is equal to orlonger than a predetermined time threshold, generate the first signal ata first level to keep the transistor turned on, the predetermined timethreshold being larger than zero in magnitude; and if the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generate the first signal at a second level to allow thetransistor to be turned on and to be turned off, the second level beingdifferent from the first level.

According to some embodiments, a method for controlling one or morelight emitting diodes, the method comprising: receiving a cathodevoltage from a cathode of a diode, the diode including an anodeconfigured to receive a rectified voltage generated by a rectifyingbridge; generating a first signal based at least in part on the cathodevoltage; receiving the first signal; generating a second signal based atleast in part on the first signal; and outputting the second signal to agate terminal of a transistor, the transistor including a sourceterminal coupled to a first resistor, the transistor further including adrain terminal coupled to the one or more light emitting diodes and anoutput capacitor connected to the cathode of the diode; wherein thegenerating a first signal based at least in part on the cathode voltageincludes: if the cathode voltage has not remained higher than apredetermined voltage threshold for a time duration that is equal to orlonger than a predetermined time threshold, generating the first signalat a first level to keep the transistor turned on, the predeterminedtime threshold being larger than zero in magnitude; and if the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generating the first signal at a second level to allow thetransistor to be turned on and to be turned off, the second level beingdifferent from the first level.

Depending upon embodiment, one or more benefits may be achieved. Thesebenefits and various additional objects, features and advantages of thepresent invention can be fully appreciated with reference to thedetailed description and accompanying drawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing an LED lighting system according tosome embodiments of the present invention.

FIG. 2 is a circuit diagram showing certain components of the powersupply controller as part of the LED lighting system as shown in FIG. 1according to certain embodiments of the present invention.

FIG. 3 is a circuit diagram showing an LED lighting system according tocertain embodiments of the present invention.

FIG. 4 shows simplified timing diagrams for the LED lighting system asshown in FIG. 1 and FIG. 2 according to some embodiments.

FIG. 5 is a diagram showing a method for the LED lighting system asshown in FIG. 1 and/or the LED lighting system as shown in FIG. 3according to some embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the present invention are directed to circuits.More particularly, some embodiments of the invention provide systems andmethods for providing power supply to current controllers. Merely by wayof example, some embodiments of the invention have been applied to lightemitting diodes (LEDs). But it would be recognized that the inventionhas a much broader range of applicability.

FIG. 1 is a circuit diagram showing an LED lighting system according tosome embodiments of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. As shown in FIG. 1 , the LED lighting system 100includes a current controller 110 (e.g., a controller chip), an LED load120 (e.g., one or more light emitting diodes), a diode 140 (e.g., D1),an output capacitor 150 (e.g., Cout), a transistor 160 (e.g., M1), and aresistor 170 (e.g., R1), and a rectifier 130 (e.g., a bridge rectifiercircuit). For example, the transistor 160 (e.g., M1) is a powertransistor. Although the above has been shown using a selected group ofcomponents for the LED lighting system, there can be many alternatives,modifications, and variations. For example, some of the components maybe expanded and/or combined. Other components may be inserted to thosenoted above. Depending upon the embodiment, the arrangement ofcomponents may be interchanged with others replaced. Further details ofthese components are found throughout the present specification.

According to certain embodiments, the current controller 110 (e.g., acontroller chip) includes a power supply controller 112 and a driver114. In some examples, the current controller 110 (e.g., a controllerchip) also includes terminals 180, 182, 184, and 186 (e.g., pins 180,182, 184, and 186). In certain examples, the power supply controller 112provides power supply to other components of the current controller 110,such as providing the power supply to the driver 114. For example, thepower supply controller 112 includes terminals 111 and 113. As anexample, the driver 114 includes terminals 115, 117, and 119.

In some embodiments, the power supply controller 112 receives a voltage190 at the terminal 111 through the terminal 180 (e.g., the HVterminal). As an example, the terminal 180 is connected to a cathode 142of the diode 140 and a terminal 152 of the output capacitor 150. Forexample, the diode 140 also includes an anode 144, which receives avoltage 192 (e.g., a rectified voltage VIN). In certain examples, therectifier 130 (e.g., a bridge rectifier circuit) of the LED lightingsystem 100 receives an AC input voltage (e.g., VAC), generates thevoltage 192 (e.g., a rectified voltage VIN), and outputs the voltage 192(e.g., a rectified voltage VIN) to the anode 144 of the diode 140. Forexample, the rectifier 130 includes a full-wave rectifier circuit. As anexample, the rectifier 130 includes an half-wave rectifier circuit. Insome examples, the terminal 113 of the power supply controller 112 isconnected to the terminal 115 of the driver 114. For example, the powersupply controller 112 outputs a signal 116 at the terminal 113, and thesignal 116 is received by the driver 114 at the terminal 115. As anexample, the signal 116 is a logic signal. In certain examples, theterminal 117 of the driver 114 is connected to a gate terminal of thetransistor 160.

In certain embodiments, the output capacitor 150 also includes aterminal 154. For example, the terminal 154 is connected to a drainterminal of the transistor 160. In some examples, the transistor 160includes the gate terminal, the drain terminal, and also a sourceterminal. As an example, the source terminal of the transistor 160 isconnected to a terminal 172 of the resistor 170, which also includes aterminal 174. For example, the terminal 174 is connected to the groundto receive the ground voltage.

According to some embodiments, the LED load 120 (e.g., one or more lightemitting diodes) includes terminals 122 and 124. In certain examples,the terminal 122 is connected to the terminal 152 of the outputcapacitor 150, and the terminal 124 is connected to the terminal 154 ofthe output capacitor 150. For example, a voltage drop 156 represents thevoltage drop between the terminal 152 of the output capacitor 150 andthe terminal 154 of the output capacitor 150. In some examples, the LEDload 120 includes multiple light emitting diodes connected in paralleland/or multiple light emitting diodes connected in series. As anexample, the LED load 120 includes one or more in-line light emittingdiodes. For example, the LED load 120 includes one or more surfacemounted light emitting diodes.

According to certain embodiments, the terminal 172 of the resistor 170is connected to the source terminal of the transistor 160 and is alsoconnected to the terminal 119 of the driver 114 through the terminal 184(e.g., CS) of the current controller 110. For example, the resistor 170generates a feedback voltage 173 at the terminal 172, and the feedbackvoltage 173 is also received by the terminal 119 of the driver 114 toform a negative feedback loop. In certain examples, during normaloperation of the LED lighting system 100, the driver 114 generates agate voltage 162 based on the feedback voltage 173, and outputs the gatevoltage 162 to the gate terminal of the transistor 160 in order tocontrol a current 194 that flows through the LED load 120. For example,during normal operation of the LED lighting system 100, the driver 114performs liner constant current control and keeps the current 194 at aconstant magnitude. In some examples, the voltage 190 changes from zeroto a peak value, and the peak value is equal to √{square root over (2)}multiplied by the root-mean-squared (RMS) value of an AC input voltage(e.g., VAC). For example, the root-mean-squared (RMS) value of the ACinput voltage (e.g., VAC) is equal to 110 volts. As an example, theroot-mean-squared (RMS) value of the AC input voltage (e.g., VAC) isequal to 220 volts.

As shown in FIG. 1 , when the LED lighting system 100 starts up, thevoltage 192 (e.g., the rectified voltage VIN) is used to provide powerto the current controller 110 (e.g., a controller chip), and the powersupply controller 112 of the current controller 110 (e.g., a controllerchip) is used to control the transistor 160 to keep the transistor 160closed (e.g., turned on) during an initial stage according to certainembodiments. For example, the initial stage lasts longer than at leastone cycle of the voltage 192 (e.g., the rectified voltage VIN). As anexample, one cycle of the voltage 192 (e.g., the rectified voltage VIN)is equal to half a cycle of the AC input voltage (e.g., VAC).

In some embodiments, during the initial stage, the transistor 160remains closed (e.g., turned on) in order to charge the output capacitor150. For example, the transistor 160 remains turned on in the linearregion during the initial stage. As an example, the transistor 160remains turned on in the saturation region during the initial stage. Incertain examples, the current controller 110 (e.g., a controller chip)is used to control a current 164 that flows through the transistor 160when the transistor 160 is turned on in order to control a chargingcurrent of the output capacitor 150 during the initial stage.

In certain embodiments, the initial stage of the LED lighting system 100ends and the normal operation stage of the LED lighting system 100starts when the output capacitor 150 is sufficiently charged so that thevoltage drop 156 of the output capacitor 150 can ensure the currentcontroller 110 (e.g., a controller chip) to operate normally withoutinterruption during the normal operation stage. As an example, duringthe normal operation stage, the LED lighting system 100 performs normaloperation. In some examples, after the initial stage of the LED lightingsystem 100 ends, the current controller 110 (e.g., a controller chip)operates normally without interruption while being powered by thevoltage 192 (e.g., a rectified voltage VIN) and/or the voltage drop 156of the output capacitor 150 during the normal operation stage. Forexample, if the voltage 192 (e.g., a rectified voltage VIN) is largerthan the voltage 190, the diode 140 is forward biased and the voltage192 (e.g., a rectified voltage VIN) provides power to the currentcontroller 110 (e.g., a controller chip). As an example, if the voltage192 (e.g., a rectified voltage VIN) is smaller than the voltage 190, thediode 140 is reverse biased and the voltage drop 156 of the outputcapacitor 150 provides power to the current controller 110 (e.g., acontroller chip).

According to some embodiments, the LED lighting system 100 operates intwo stages including the initial stage and the normal operation stage.In certain examples, during the initial stage, the transistor 160remains turned on. For example, the current controller 110 (e.g., acontroller chip) is powered by the voltage 192 (e.g., a rectifiedvoltage VIN) during the initial stage. In some examples, the initialstage of the LED lighting system 100 ends and the normal operation stageof the LED lighting system 100 starts when the voltage drop 156 of theoutput capacitor 150 becomes able to ensure the current controller 110(e.g., a controller chip) to operate normally without interruptionduring the normal operation stage. For example, during the normaloperation stage, the current controller 110 (e.g., a controller chip)operates normally without interruption while being powered by thevoltage 192 (e.g., a rectified voltage VIN) and/or the voltage drop 156of the output capacitor 150. As an example, if the voltage 192 (e.g., arectified voltage VIN) is larger than the voltage 190, the diode 140 isforward biased and the voltage 192 (e.g., a rectified voltage VIN)provides power to the current controller 110 (e.g., a controller chip),and if the voltage 192 (e.g., a rectified voltage VIN) is smaller thanthe voltage 190, the diode 140 is reverse biased and the voltage drop156 of the output capacitor 150 provides power to the current controller110 (e.g., a controller chip).

As discussed above and further emphasized here, FIG. 1 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In some embodiments, the LED lighting system 100 alsoincludes a rectifier (e.g., a bridge rectifier circuit) that generatesthe voltage 192 (e.g., a rectified voltage VIN). For example, therectifier of the LED lighting system 100 receives an AC input voltage(e.g., VAC) and generates the voltage 192 (e.g., a rectified voltageVIN). As an example, the rectifier of the LED lighting system 100includes a full-wave rectifier circuit and/or an half-wave rectifiercircuit. In certain embodiments, the resistor 170 (e.g., R1) includesmultiple resistors in series and/or multiple resistors in parallel.

FIG. 2 is a circuit diagram showing certain components of the powersupply controller 112 as part of the LED lighting system 100 as shown inFIG. 1 according to certain embodiments of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 2 , thepower supply controller 112 includes a voltage generator 210, an initialstage controller 220, a voltage detector 230, and a timer 240. Althoughthe above has been shown using a selected group of components for theLED lighting system, there can be many alternatives, modifications, andvariations. For example, some of the components may be expanded and/orcombined. Other components may be inserted to those noted above.Depending upon the embodiment, the arrangement of components may beinterchanged with others replaced. Further details of these componentsare found throughout the present specification.

In some embodiments, the voltage generator 210 and the initial stagecontroller 220 (e.g., an operation controller) are configured to keepthe transistor 160 (e.g., M1) closed (e.g., turned off) during theinitial stage. In certain embodiments, the voltage detector 230 and thetimer 240 are configured to determine whether the voltage drop 156 ofthe terminal 152 of the output capacitor 150 becomes able to ensure thecurrent controller 110 (e.g., a controller chip) to operate normallywithout interruption, so that the LED lighting system 100 changes fromthe initial stage to the normal operation stage.

According to some embodiments, the voltage generator 210 receives thevoltage 190 and generates a voltage 212 (e.g., VDD). For example, thevoltage 212 (e.g., VDD) is received as power supply by one or morecomponents of the current controller 110 (e.g., a controller chip). Incertain examples, the voltage 212 (e.g., VDD) is received as powersupply by the initial stage controller 220 (e.g., an operationcontroller), and the initial stage controller 220 (e.g., an operationcontroller) is coupled to the voltage generator 210. For example, theinitial stage controller 220 also receives a signal 242 and generatesthe signal 116 (e.g., MOS_ini). As an example, the signal 116 (e.g.,MOS_ini) is a logic signal.

According to certain embodiments, the signal 116 (e.g., MOS_ini) isreceived by the driver 114. As an example, the power supply controller112 generates the signal 116 (e.g., MOS_ini) and outputs the signal 116(e.g., MOS_ini) to the driver 114. For example, the driver 114 generatesthe gate voltage 162 based at least in part on the signal 116 (e.g.,MOS_ini). In some examples, the gate voltage 162 is received by the gateterminal of the transistor 160. As an example, the transistor 160 is anNMOS transistor, and if the gate voltage 162 is at a high voltage level,the transistor 160 is turned on to form a conducting path to the groundfor charging the output capacitor 150.

In some embodiments, the voltage detector 230 receives the voltage 190,detects the received voltage 190, determines whether the detectedvoltage 190 is larger than an operation voltage threshold of the currentcontroller 110 (e.g., a controller chip), and generates a signal 232(e.g., UVLO_off). In some examples, the operation voltage threshold(e.g., the voltage threshold 432 as shown in FIG. 4 ) of the currentcontroller 110 (e.g., a controller chip) represents the minimum powersupply (e.g., the minimum voltage) that the current controller 110 needsin order to operate normally. For example, if the voltage 190 is higherthan the operation voltage threshold, the current controller 110 canoperate normally. As an example, if the voltage 190 is lower than theoperation voltage threshold, the current controller 110 cannot operatenormally. In certain examples, if the detected voltage 190 is largerthan the operation voltage threshold of the current controller 110(e.g., a controller chip), the voltage detector 230 generates the signal232 (e.g., UVLO_off) at a logic high level. As an example, if thedetected voltage 190 is not larger than the operation voltage thresholdof the current controller 110 (e.g., a controller chip), the voltagedetector 230 generates the signal 232 (e.g., UVLO_off) at a logic lowlevel.

In certain embodiments, the signal 232 (e.g., UVLO_off) is received bythe timer 240, which is configured to generate the signal 242 based atleast in part on the signal 232 (e.g., UVLO_off). For example, if thesignal 232 (e.g., UVLO_off) changes from the logic low level to thelogic high level, the timer 240 starts counting. As an example, if thesignal 232 (e.g., UVLO_off) changes from the logic high level to thelogic low level, the timer 240 is rest to zero. In some examples, if thesignal 232 (e.g., UVLO_off) changes from the logic low level to thelogic high level, the timer 240 starts counting the time duration duringwhich the signal 232 (e.g., UVLO_off) remains at the logic high level.For example, if the counted time duration becomes larger than apredetermined time threshold (e.g., the threshold duration T_(th) asshown in FIG. 4 ), the timer 240 changes the signal 242 from the logiclow level to the logic high level. As an example, the predetermined timethreshold (e.g., the threshold duration T_(th) as shown in FIG. 4 ) islarger than zero. In certain examples, the predetermined time thresholdis longer than at least one cycle of the voltage 192 (e.g., therectified voltage VIN) in duration. For example, the timer 240 measuresthe counted time duration by the number of cycles of the voltage 192(e.g., the rectified voltage VIN). As an example, the timer 240 measuresthe counted time duration by an internal clock of the time 240.

According to some embodiments, the initial stage controller 220 receivesthe signal 242 and generates the signal 116 (e.g., MOS_ini) based atleast in part on the signal 242. For example, if the signal 242 changesfrom the logic low level to the logic high level, the initial stagecontroller 220 ends the initial stage of the LED lighting system 100 andstarts the normal operation stage of the LED lighting system 100. As anexample, during the normal operation stage of the LED lighting system100, the driver 114 generates the gate voltage 162 based at least inpart on the feedback voltage 173 to regulate the current 194 (e.g., tokeep the current 194 at a predetermined magnitude).

According to certain embodiments, the voltage generator 210 includes ajunction field-effect transistor (JFET) and/or a low dropout regulator(LDO). According to some embodiments, the transistor 160 (e.g., M1)includes a metal oxide semiconductor (e.g., MOS) transistor and/or abipolar junction transistor. In certain examples, if the signal 116(e.g., MOS_ini) is at the logic high level, the driver 114 does notchange the gate voltage 162 so that the transistor 160 (e.g., M1)remains turned on. For example, the transistor 160 is an NMOStransistor, and if the signal 116 (e.g., MOS_ini) is at the logic highlevel, the driver 114 keeps the gate voltage 162 at the logic high levelso that the transistor 160 (e.g., M1) remains turned on. In someexamples, if the signal 116 (e.g., MOS_ini) is at the logic low level,the driver 114 changes the gate voltage 162 so that the transistor 160(e.g., M1) changes between being turned on and being turned off in orderto regulate the current 194 (e.g., to keep the current 194 at apredetermined magnitude) based at least in part on the feedback voltage173.

As discussed above and further emphasized here, FIG. 1 and FIG. 2 aremerely examples, which should not unduly limit the scope of the claims.One of ordinary skill in the art would recognize many variations,alternatives, and modifications. In some embodiments, the LED lightingsystem 100 also includes a rectifier (e.g., a bridge rectifier circuit)that generates the voltage 192 (e.g., a rectified voltage VIN). Forexample, the rectifier of the LED lighting system 100 receives an ACinput voltage (e.g., VAC) and generates the voltage 192 (e.g., arectified voltage VIN). As an example, the rectifier of the LED lightingsystem 100 includes a full-wave rectifier circuit and/or an half-waverectifier circuit. In certain embodiments, the LED lighting system 100also includes a dummy resistor

FIG. 3 is a circuit diagram showing an LED lighting system according tocertain embodiments of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. As shown in FIG. 3 , the LED lighting system 300includes a current controller 310 (e.g., a controller chip), an LED load320 (e.g., one or more light emitting diodes), a diode 340 (e.g., D1),an output capacitor 350 (e.g., Cout), a transistor 360 (e.g., M1), aresistor 370 (e.g., R1), a resistor 332 (e.g., Rdummy), and a rectifier330 (e.g., a bridge rectifier circuit). For example, the transistor 360(e.g., M1) is a power transistor. Although the above has been shownusing a selected group of components for the LED lighting system, therecan be many alternatives, modifications, and variations. For example,some of the components may be expanded and/or combined. Other componentsmay be inserted to those noted above. Depending upon the embodiment, thearrangement of components may be interchanged with others replaced.Further details of these components are found throughout the presentspecification.

According to certain embodiments, the current controller 310 (e.g., acontroller chip) includes a power supply controller 312 and a driver314. In some examples, the current controller 310 (e.g., a controllerchip) also includes terminals 380, 382, 384, and 386 (e.g., pins 380,382, 384, and 386). In certain examples, the power supply controller 312provides power supply to other components of the current controller 310,such as providing the power supply to the driver 314. For example, thepower supply controller 312 includes terminals 311 and 313. As anexample, the driver 314 includes terminals 315, 317, and 319.

In some embodiments, the power supply controller 312 receives a voltage390 at the terminal 311 through the terminal 380 (e.g., the HVterminal). As an example, the terminal 380 is connected to a cathode 342of the diode 340 and a terminal 352 of the output capacitor 350. Forexample, the diode 340 also includes an anode 344, which receives avoltage 392 (e.g., a rectified voltage VIN). In certain examples, therectifier 330 (e.g., a bridge rectifier circuit) of the LED lightingsystem 300 receives an AC input voltage (e.g., VAC), generates thevoltage 392 (e.g., a rectified voltage VIN), and outputs the voltage 392(e.g., a rectified voltage VIN) to the anode 344 of the diode 340. Forexample, the rectifier 330 includes a full-wave rectifier circuit. As anexample, the rectifier 330 includes an half-wave rectifier circuit. Insome examples, the terminal 313 of the power supply controller 312 isconnected to the terminal 315 of the driver 314. For example, the powersupply controller 312 outputs a signal 316 at the terminal 313, and thesignal 316 is received by the driver 314 at the terminal 315. As anexample, the signal 316 is a logic signal. In certain examples, theterminal 317 of the driver 314 is connected to a gate terminal of thetransistor 360.

In certain embodiments, the output capacitor 350 also includes aterminal 354. For example, the terminal 354 is connected to a drainterminal of the transistor 360. In some examples, the resistor 332(e.g., Rdummy) includes terminals 334 and 336. For example, the terminal334 of the resistor 332 is connected to the terminal 352 of the outputcapacitor 350. As an example, the terminal 336 of the resistor 332 isconnected to the terminal 354 of the output capacitor 350. In certainexamples, the transistor 360 includes the gate terminal, the drainterminal, and also a source terminal. As an example, the source terminalof the transistor 360 is connected to a terminal 372 of the resistor370, which also includes a terminal 374. For example, the terminal 374is connected to the ground to receive the ground voltage.

According to some embodiments, the LED load 320 (e.g., one or more lightemitting diodes) includes terminals 322 and 324. In certain examples,the terminal 322 is connected to the terminal 352 of the outputcapacitor 350, and the terminal 324 is connected to the terminal 354 ofthe output capacitor 350. For example, the terminal 352 of the outputcapacitor 350 is at a voltage 356. In some examples, the LED load 320includes multiple light emitting diodes connected in parallel and/ormultiple light emitting diodes connected in series. As an example, theLED load 320 includes one or more in-line light emitting diodes. Forexample, the LED load 320 includes one or more surface mounted lightemitting diodes.

According to certain embodiments, the terminal 372 of the resistor 370is connected to the source terminal of the transistor 360 and is alsoconnected to the terminal 319 of the driver 314 through the terminal 384(e.g., CS) of the current controller 310. For example, the resistor 370generates a feedback voltage 373 at the terminal 372, and the feedbackvoltage 373 is received by the terminal 319 of the driver 314 to form anegative feedback loop. In certain examples, during normal operation ofthe LED lighting system 300, the driver 314 generates a gate voltage 362based on the feedback voltage 373, and outputs the gate voltage 362 tothe gate terminal of the transistor 360 in order to control a current396 that flows through the transistor 360, and the current 396 isapproximately equal to the current 394 that flows through the LED load320. For example, during normal operation of the LED lighting system300, the driver 314 performs liner constant current control and keepsthe current 394 at a constant magnitude. In some examples, the voltage390 changes from zero to a peak value, and the peak value is equal to√{square root over (2)} multiplied by the root-mean-squared (RMS) valueof an AC input voltage (e.g., VAC). For example, the root-mean-squared(RMS) value of the AC input voltage (e.g., VAC) is equal to 110 volts.As an example, the root-mean-squared (RMS) value of the AC input voltage(e.g., VAC) is equal to 220 volts.

As shown in FIG. 3 , when the LED lighting system 300 starts up, thevoltage 392 (e.g., the rectified voltage VIN) is used to provide powerto the current controller 310 (e.g., a controller chip), and the powersupply controller 312 of the current controller 310 (e.g., a controllerchip) is used to control the transistor 360 to keep the transistor 360closed (e.g., turned on) during an initial stage according to certainembodiments. For example, the initial stage lasts longer than at leastone cycle of the voltage 392 (e.g., the rectified voltage VIN). As anexample, one cycle of the voltage 392 (e.g., the rectified voltage VIN)is equal to half a cycle of the AC input voltage (e.g., VAC).

In some embodiments, during the initial stage, the transistor 360remains closed (e.g., turned on) in order to charge the output capacitor350. For example, the transistor 360 remains turned on in the linearregion during the initial stage. As an example, the transistor 160remains turned on in the saturation region during the initial stage. Incertain examples, the current controller 310 (e.g., a controller chip)is used to control a current 364 that flows through the transistor 360when the transistor 360 is turned on in order to control a chargingcurrent of the output capacitor 350 during the initial stage.

In certain embodiments, the initial stage of the LED lighting system 300ends and the normal operation stage of the LED lighting system 300starts when the output capacitor 350 is sufficiently charged so that thevoltage 356 of the output capacitor 350 can ensure the currentcontroller 310 (e.g., a controller chip) to operate normally withoutinterruption during the normal operation stage. As an example, duringthe normal operation stage, the LED lighting system 300 performs normaloperation. In some examples, after the initial stage of the LED lightingsystem 300 ends, the current controller 310 (e.g., a controller chip)operates normally without interruption while being powered by thevoltage 392 (e.g., a rectified voltage VIN) and/or the voltage 356 ofthe output capacitor 350 during the normal operation stage. For example,if the voltage 392 (e.g., a rectified voltage VIN) is larger than thevoltage 356 of the output capacitor 350, the diode 340 is forward biasedand the voltage 392 (e.g., a rectified voltage VIN) provides power tothe current controller 310 (e.g., a controller chip). As an example, ifthe voltage 392 (e.g., a rectified voltage VIN) is smaller than thevoltage 356 of the output capacitor 350, the diode 340 is reverse biasedand the voltage 356 of the output capacitor 350 provides power to thecurrent controller 310 (e.g., a controller chip).

According to some embodiments, the LED lighting system 300 operates intwo stages including the initial stage and the normal operation stage.In certain examples, during the initial stage, the transistor 360remains turned on. For example, the current controller 310 (e.g., acontroller chip) is powered by the voltage 392 (e.g., a rectifiedvoltage VIN) during the initial stage. In some examples, the initialstage of the LED lighting system 300 ends and the normal operation stageof the LED lighting system 300 starts when the voltage 356 of the outputcapacitor 350 becomes able to ensure the current controller 310 (e.g., acontroller chip) to operate normally without interruption during normaloperation stage. For example, during the normal operation stage, thecurrent controller 310 (e.g., a controller chip) operates normallywithout interruption while being powered by the voltage 392 (e.g., arectified voltage VIN) and/or the voltage 356 of the output capacitor350. As an example, if the voltage 392 (e.g., a rectified voltage VIN)is larger than the voltage 356 of the output capacitor 350, the diode340 is forward biased and the voltage 392 (e.g., a rectified voltageVIN) provides power to the current controller 310 (e.g., a controllerchip), and if the voltage 392 (e.g., a rectified voltage VIN) is smallerthan the voltage 356 of the output capacitor 350, the diode 340 isreverse biased and the voltage 356 of the output capacitor 350 providespower to the current controller 310 (e.g., a controller chip).

According to certain embodiments, the current controller 310 (e.g., acontroller chip) is the same as the current controller 110 (e.g., acontroller chip), the LED load 320 (e.g., one or more light emittingdiodes) is the same as the LED load 120 (e.g., one or more lightemitting diodes), the diode 340 (e.g., D1) is the same as the diode 140(e.g., D1), the output capacitor 350 (e.g., Cout) is the same as theoutput capacitor 150 (e.g., Cout), the transistor 360 (e.g., M1) is thesame as the transistor 160 (e.g., M1), and the resistor 370 (e.g., R1)is the same as the resistor 170 (e.g., R1). For example, the powersupply controller 312 is the same as the power supply controller 112,and the driver 314 is the same as the driver 114. As an example, thepower supply controller 312 includes the voltage generator 210, theinitial stage controller 220, the voltage detector 230, and the timer240.

As discussed above and further emphasized here, FIG. 3 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In certain embodiments, the resistor 370 (e.g., R1)includes multiple resistors in series and/or multiple resistors inparallel.

FIG. 4 shows simplified timing diagrams for the LED lighting system 100as shown in FIG. 1 and FIG. 2 according to some embodiments. Thesediagrams are merely examples, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 3 , thewaveform 410 represents the voltage 192 (e.g., the rectified voltageVIN) as a function of time, the waveform 420 represents the voltage drop156 of the output capacitor 150 as a function of time, the waveform 430represents the voltage 190 as a function of time, the waveform 440represents the voltage 212 (e.g., VDD) as a function of time, thewaveform 450 represents the signal 232 (e.g., UVLO_off) as a function oftime, the waveform 460 represents the signal 242 as a function of time,and the waveform 470 represents the signal 116 (e.g., MOS_ini) as afunction of time.

As shown by the waveform 410, the voltage 192 (e.g., the rectifiedvoltage VIN) changes as a function of time according to certainembodiments. For example, cycle A, cycle B, cycle C, cycle D, and cycleE each represents one cycle of the voltage 192 (e.g., the rectifiedvoltage VIN). As an example, one cycle of the voltage 192 (e.g., therectified voltage VIN) is equal to half a cycle of the AC input voltage(e.g., VAC).

As shown by the waveform 420, the voltage drop 156 of the outputcapacitor 150 changes as a function of time according to someembodiments. In certain examples, the voltage drop 156 increases inmagnitude when the output capacitor 150 is being charged during theinitial stage of the LED lighting system 100. For example, during theinitial stage with the transistor 160 turned on, if the voltage 192(e.g., a rectified voltage VIN) is larger than the voltage 190, thediode 140 is forward biased and the voltage 192 (e.g., a rectifiedvoltage VIN) is used to charge the output capacitor 150 to increase thevoltage drop 156. As an example, during the initial stage with thetransistor 160 turned on, if the voltage 192 (e.g., a rectified voltageVIN) is smaller than the voltage 190, the diode 140 is reverse biasedand the voltage 192 (e.g., a rectified voltage VIN) is not used tocharge the output capacitor 150 so the voltage drop 156 remainsunchanged.

As shown by the waveform 430, the voltage 190 changes as a function oftime according to certain embodiments. For example, the voltage 190falls below a voltage threshold 432 (e.g., the operation voltagethreshold) at time t₁, remains below the voltage threshold 432 (e.g.,the operation voltage threshold) from time t₁ to time t₂, and risesabove the voltage threshold 432 (e.g., the operation voltage threshold)at time t₂. As an example, the voltage 190 falls below the voltagethreshold 432 (e.g., the operation voltage threshold) at time t₃,remains below the voltage threshold 432 (e.g., the operation voltagethreshold) from time t₃ to time t₄, and rises above the voltagethreshold 432 (e.g., the operation voltage threshold) at time t₄. Forexample, the voltage 190 falls below the voltage threshold 432 (e.g.,the operation voltage threshold) at time t₅, remains below the voltagethreshold 432 (e.g., the operation voltage threshold) from time t₅ totime t₆, and rises above the voltage threshold 432 (e.g., the operationvoltage threshold) at time t₆.

In some examples, the voltage threshold 432 (e.g., the operation voltagethreshold of the current controller 110) represents the minimum powersupply (e.g., the minimum voltage) that the current controller 110 needsin order to operate normally. For example, if the voltage 190 is higherthan the voltage threshold 432 (e.g., the operation voltage threshold),the current controller 110 can operate normally. As an example, if thevoltage 190 is lower than the voltage threshold 432 (e.g., the operationvoltage threshold), the current controller 110 cannot operate normally.

As shown by the waveform 440, the voltage 212 (e.g., VDD) changes as afunction of time according to some embodiments. In certain examples, thevoltage 212 (e.g., VDD) is at a high voltage level 442 if the voltage190 is higher than the voltage threshold 432 (e.g., the operationvoltage threshold), and the voltage 212 (e.g., VDD) is at a low voltagelevel 444 if the voltage 190 is higher than the voltage threshold 432(e.g., the operation voltage threshold). For example, the voltage level444 changes with time. In some examples, the voltage 212 (e.g., VDD)changes from the high voltage level 442 to the low voltage level 444 attime t₁, changes from the low voltage level 444 to the high voltagelevel 442 at time t₂, changes from the high voltage level 442 to the lowvoltage level 444 at time t₃, changes from the low voltage level 444 tothe high voltage level 442 at time t₄, changes from the high voltagelevel 442 to the low voltage level 444 at time t₅, and changes from thelow voltage level 444 to the high voltage level 442 at time t₆.

As shown by the waveform 450, the signal 232 (e.g., UVLO_off) changes asa function of time according to some embodiments. In certain examples,the signal 232 (e.g., UVLO_off) is at a logic high level if the voltage190 is higher than the voltage threshold 432 (e.g., the operationvoltage threshold), and the signal 232 (e.g., UVLO_off) is at a logiclow level if the voltage 190 is higher than the voltage threshold 432(e.g., the operation voltage threshold). In some examples, the signal232 (e.g., UVLO_off) changes from the logic high level to the logic lowlevel at time t₁, changes from the logic low level to the logic highlevel at time t₂, changes from the logic high level to the logic lowlevel at time t₃, changes from the logic low level to the logic highlevel at time t₄, changes from the logic high level to the logic lowlevel at time t₅, and changes from the logic low level to the logic highlevel at time t₆.

As shown by the waveform 460, the signal 242 changes as a function oftime according to certain embodiments. In certain examples, unless thesignal 232 (e.g., UVLO_off) remains at the logic high level for a timeduration that is equal to or longer than a threshold duration T_(th)(e.g., the predetermined time threshold), the signal 242 is at the logiclow level. As an example, the threshold duration T_(th) is larger thanzero. For example, if the signal 232 (e.g., UVLO_off) remains at thelogic high level for a time duration that is equal to or longer than thethreshold duration T_(th) (e.g., the predetermined time threshold), thesignal 242 is at the logic high level. As an example, the thresholdduration T_(th) (e.g., the predetermined time threshold) is longer thanat least one cycle of the voltage 192 (e.g., the rectified voltage VIN)as shown by the waveform 410.

In some examples, the signal 242 is at the logic low level from time t₁to time t₂ in response to the signal 232 (e.g., UVLO_off) being at thelogic low level from time t₁ to time t₂. For example, the signal 242 isat the logic low level from time t₂ to time t₃ in response to the signal232 (e.g., UVLO_off) being at the logic high level from time t₂ to timet₃ but changing to the logic low level at time t₃, wherein the timeduration from time t₂ to time t₃ is shorter than the threshold durationT_(th) (e.g., the predetermined time threshold). As an example, thesignal 242 changes from the logic low level to the logic high level attime t₇ in response to the signal 232 (e.g., UVLO_off) remains at thelogic high level from time t₆ to time t₇, wherein the time duration fromtime t₆ to time t₇ is equal to the threshold duration T_(th) (e.g., thepredetermined time threshold). In certain examples, the signal 242remains at the logic high level after time t₇ in response to the signal232 (e.g., UVLO_off) remaining at the logic high level since time t₆. Asan example, at a time after time t₇, if the signal 232 (e.g., UVLO_off)changes from the logic high level to the logic low level, the signal 242changes from the logic high level to the logic low level.

As shown by the waveform 470, the signal 116 (e.g., MOS_ini) changes asa function of time according to some embodiments. In certain examples,the signal 116 (e.g., MOS_ini) is at the logic high level if the signal242 is at the logic low level, and the signal 116 (e.g., MOS_ini) is atthe logic low level if the signal 242 is at the logic high level. Forexample, from time t₁ to time t₇, in response to the signal 242remaining at the logic low level, the signal 116 (e.g., MOS_ini) remainsat the logic high level. As an example, at time t₇, in response to thesignal 242 changing from the logic low level to the logic high level,the signal 116 (e.g., MOS_ini) changes from the logic high level to thelogic low level. For example, after time t₇, in response to the signal242 remaining at the logic high level, the signal 116 (e.g., MOS_ini)remains at the logic low level. In some examples, if the signal 242 isat the logic high level, the LED lighting system 100 is in the initialstage, and if the signal 242 is at the logic low level, the LED lightingsystem 100 is in the normal operation stage. For example, from time t₁to time t₇, the signal 242 remains at the logic high level and the LEDlighting system 100 is in the initial stage. As an example, at time t₇,the signal 242 changes from the logic high level to the logic low leveland the LED lighting system 100 changes from the initial stage to thenormal operation stage. For example, after time t₇, the signal 242remains at the logic low level and the LED lighting system 100 is in thenormal operation stage.

In certain embodiments, during the initial stage of the LED lightingsystem 100, the driver 114 generates the gate voltage 162 to keep thetransistor 160 turned on in order to charge the output capacitor 150. Insome embodiments, during the normal operation stage of the LED lightingsystem 100, the driver 114 generates the gate voltage 162 to change thetransistor 160 between being turned on and being turned off based atleast in part on the feedback voltage 173 in order to regulate thecurrent 194 (e.g., to keep the current 194 at a predeterminedmagnitude).

In some embodiments, from time t₆ to time t₇, the voltage 190 remainshigher than the voltage threshold 432 (e.g., the operation voltagethreshold) as shown by the waveform 430, the voltage 212 (e.g., VDD)remains at the high voltage level 442 as shown by the waveform 440, andthe signal 232 (e.g., UVLO_off) remains at the logic high level by thewaveform 450. For example, at time t₇, the voltage 190 has remainedhigher than the voltage threshold 432 (e.g., the operation voltagethreshold) for a time duration that is no less than the thresholdduration T_(th) (e.g., the predetermined time threshold). As an example,at time t₇, the signal 232 (e.g., UVLO_off) changes from the logic lowlevel to the logic high level as shown by the waveform 460, and thesignal 116 (e.g., MOS_ini) changes from the logic high level to thelogic low level as shown by the waveform 470. In certain examples, thethreshold duration T_(th) (e.g., the predetermined time threshold) islonger than at least one cycle of the voltage 192 (e.g., the rectifiedvoltage VIN) as shown by the waveform 410, so if the voltage 190 hasremained higher than the voltage threshold 432 (e.g., the operationvoltage threshold) for a time duration that is no less than thethreshold duration T_(th) (e.g., the predetermined time threshold), thevoltage 190 remains higher than the voltage threshold 432 (e.g., theoperation voltage threshold) when the voltage 192 (e.g., a rectifiedvoltage VIN) is small (e.g., when the voltage 192 reaches the valleyduring the cycle of the voltage 192).

As shown in FIG. 4 , during the initial stage of the LED lighting system100, the signal 116 (e.g., MOS_ini) remains at the logic high level(e.g., from time t₁ to time t₇ as shown by the waveform 470) accordingto some embodiments. In certain examples, the signal 116 (e.g., MOS_ini)at the logic high level is received by the driver 114, which in responsegenerates the gate voltage 162 to keep the transistor 160 turned onduring the initial stage (e.g., to keep the transistor 160 turned onfrom time t₁ to time t₇) so that the output capacitor 150 can be chargedwhen the diode 140 is forward biased (e.g., when the voltage 192 islarger than the voltage 190). In some examples, from time t₁ to time t₆,the voltage drop 156 of the output capacitor 150 cannot ensure thevoltage 190 remains higher than the voltage threshold 432 (e.g., theoperation voltage threshold) when the voltage 192 (e.g., a rectifiedvoltage VIN) is small (e.g., when the voltage 192 reaches the valleyduring one cycle of the voltage 192). For example, from time t₁ to timet₂, from time t₃ to time t₄, and/or from time is to time t₆, the voltage190 is lower than the voltage threshold 432 (e.g., the operation voltagethreshold), and the voltage 212 (e.g., VDD) is at the low voltage level444 as shown by the waveforms 430 and 440.

As discussed above and further emphasized here, FIG. 4 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, FIG. 4 shows simplified timing diagramsfor the LED lighting system 300 as shown in FIG. 3 according to someembodiments.

FIG. 5 is a diagram showing a method for the LED lighting system 100 asshown in FIG. 1 and/or the LED lighting system 300 as shown in FIG. 3according to some embodiments of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The method 500 includes aprocess 510 for charging an output capacitor to increase a voltage dropof the output capacitor by keeping a transistor turned on, a process 520for determining whether the voltage drop of the output capacitor issufficient to support normal operation of a current controller, and aprocess 530 for using an input voltage and/or the voltage drop of theoutput capacitor as power supply to maintain normal operation of thecurrent controller while allowing the transistor to be turned on andturned off.

At the process 510, the output capacitor (e.g., the output capacitor 150and/or the output capacitor 350) is charged to increase the voltage dropof the output capacitor (e.g., the voltage drop 156 of the outputcapacitor 150 and/or the voltage drop 356 of the output capacitor 350)by keeping the transistor (e.g., the transistor 160 and/or thetransistor 360) turned on according to certain embodiments. For example,at the process 510, the LED lighting system 100 and/or the LED lightingsystem 300 operates in the initial stage. As an example, the process 510is performed at any time from time t₁ to time t₇.

At the process 520, it is determined whether the voltage drop of theoutput capacitor (e.g., the voltage drop 156 and/or the voltage drop356) is sufficient to support normal operation of the current controller(e.g., the current controller 110 and/or the current controller 310)according to some embodiments. In certain examples, at the process 520,it is determined whether the LED lighting system 100 and/or the LEDlighting system 300 needs to continue operating in the initial stage orneeds to start operating in the normal operation stage. For example, ifit is determined that the LED lighting system 100 and/or the LEDlighting system 300 needs to continue operating in the initial stage,the process 510 is performed. As an example, if it is determined thatthe LED lighting system 100 and/or the LED lighting system 300 needs tostart operating in the normal operation stage, the process 530 isperformed.

For example, at the time when the process 520 is performed, if thevoltage 190 or the voltage 390 has remained higher than the operationvoltage threshold (e.g., the voltage threshold 432) for a time durationthat is equal to the predetermined time threshold (e.g., the thresholdduration T_(th)), the voltage drop of the output capacitor (e.g., thevoltage drop 156 and/or the voltage drop 356) is determined to besufficient to support normal operation of the current controller (e.g.,the current controller 110 and/or the current controller 310). As anexample, at the time when the process 520 is performed, if the voltage190 or the voltage 390 has not remained higher than the operationvoltage threshold (e.g., the voltage threshold 432) for a time durationthat is equal to the predetermined time threshold (e.g., the thresholdduration T_(th), the voltage drop of the output capacitor (e.g., thevoltage drop 156 and/or the voltage drop 356) is determined to be notsufficient to support normal operation of the current controller (e.g.,the current controller 110 and/or the current controller 310).

In some examples, if it is determined that the voltage drop of theoutput capacitor (e.g., the voltage drop 156 and/or the voltage drop356) is not sufficient to support normal operation of the currentcontroller (e.g., the current controller 110 and/or the currentcontroller 310), the process 510 is performed. In certain examples, ifit is determined that the voltage drop of the output capacitor (e.g.,the voltage drop 156 and/or the voltage drop 356) is sufficient tosupport normal operation of the current controller (e.g., the currentcontroller 110 and/or the current controller 310), the process 530 isperformed.

At the process 530, the input voltage (e.g. the rectified voltage 192and/or the rectified voltage 392) and/or the voltage drop of the outputcapacitor is used as power supply to maintain normal operation of thecurrent controller (e.g., the current controller 110 and/or the currentcontroller 310) while allowing the transistor (e.g., the transistor 160and/or the transistor 360) to be turned on and turned off according tocertain embodiments. In some examples, at the process 530, the normaloperation of the LED lighting system 100 and/or the LED lighting system300 is performed. As an example, under the normal operation of the LEDlighting system 100, the driver 114 generates the gate voltage 162 tochange the transistor 160 between being turned on and being turned offin order to regulate the current 194 (e.g., to keep the current 194 at apredetermined magnitude) based at least in part on the feedback voltage173. For example, under the normal operation of the LED lighting system300, the driver 314 generates the gate voltage 362 to change thetransistor 360 between being turned on and being turned off in order toregulate the current 394 (e.g., to keep the current 394 at apredetermined magnitude) based at least in part on the feedback voltage373.

According to some embodiments, systems and methods provide power supplyto a current controller associated with LED lighting, so that duringnormal operation of the current controller, if the input voltage (e.g.,the rectified voltage) is not sufficiently large, the voltage drop ofthe output capacitor can be used to provide power supply to the currentcontroller. For example, the systems and methods for providing the powersupply do not need to use an extra external capacitor, thus loweringcosts related to bill of material (BOM). As an example, the systems andmethods for providing the power supply can ensure the normal operationof the current controller without interruption even when the inputvoltage (e.g., the rectified voltage) falls below the operation voltagethreshold of the current controller. According to certain embodiments,systems and methods provide power supply to a current controllerassociated with LED lighting, so that during normal operation of thecurrent controller, the input voltage (e.g., the rectified voltage) orthe voltage drop of the output capacitor is used to provide power supplyto the current controller.

According to certain embodiments, a system for controlling one or morelight emitting diodes includes: a power supply controller configured toreceive a cathode voltage from a cathode of a diode, the diode includingan anode configured to receive a rectified voltage generated by arectifying bridge, the power supply controller being further configuredto generate a first signal based at least in part on the cathodevoltage; and a driver configured to receive the first signal andgenerate a second signal based at least in part on the first signal, thedriver being further configured to output the second signal to a gateterminal of a transistor, the transistor including a source terminalcoupled to the driver and a first resistor, the transistor furtherincluding a drain terminal coupled to the one or more light emittingdiodes and an output capacitor connected to the cathode of the diode;wherein the power supply controller and the driver are furtherconfigured to: if the cathode voltage has not remained higher than apredetermined voltage threshold for a time duration that is equal to orlonger than a predetermined time threshold, generate the first signal ata first level to keep the transistor turned on, the predetermined timethreshold being larger than zero in magnitude; and if the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generate the first signal at a second level to allow thetransistor to be turned on and to be turned off, the second level beingdifferent from the first level. For example, the system is implementedaccording to at least FIG. 1 , FIG. 2 , FIG. 3 , FIG. 4 , and/or FIG. 5.

In some examples, the predetermined time threshold is longer than atleast one cycle of the rectified voltage in duration. In certainexamples, the power supply controller and the driver are furtherconfigured to, if the cathode voltage has not remained higher than thepredetermined voltage threshold for the time duration that is equal toor longer than the predetermined time threshold, keep the transistorturned on to charge the output capacitor. In some examples, the powersupply controller includes: a voltage generator configured to receivethe cathode voltage; an operation controller coupled to the voltagegenerator and configured to generate the first signal; a voltagedetector configured to receive the cathode voltage, determine whetherthe cathode voltage is higher than the predetermined voltage threshold,and generate a third signal indicating whether the cathode voltage ishigher than the predetermined voltage threshold; and a timer configuredto receive the third signal and generate a timer signal, the timersignal indicating whether the cathode voltage has remained higher thanthe predetermined voltage threshold for the time duration that is equalto or longer than the predetermined time threshold.

In certain examples, the operation controller is further configured toreceive the timer signal and generate the first signal based at least inpart on the timer signal. In some examples, the operation controller isfurther configured to: if the timer signal indicates that the cathodevoltage has not remained higher than the predetermined voltage thresholdfor the time duration that is equal to or longer than the predeterminedtime threshold, generate the first signal at the first level to keep thetransistor turned on; and if the timer signal indicates that the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generate the first signal at the second level to allow thetransistor to be turned on and to be turned off. In certain examples,the driver is further configured to: if the first signal is at the firstlevel, generate the second signal at a third level to turn on thetransistor; and if the first signal is at the second level, change thesecond signal from the third level to a fourth level to turn off thetransistor or from the fourth level to the third level to turn on thetransistor.

In some examples, the transistor is an NMOS transistor; the third levelcorresponds to a high voltage level; and the fourth level corresponds toa low voltage level, the low voltage being lower than the high voltagelevel. In certain examples, the diver is further configured to: receivea feedback signal from the first resistor; and if the first signal is atthe second level, change, based at least in part on the feedback signal,the second signal from the third level to the fourth level to turn offthe transistor or from the fourth level to the third level to turn onthe transistor. In some examples, the diver is further configured to: ifthe first signal is at the second level, change the second signal, basedat least in part on the feedback signal, from the third level to thefourth level to turn off the transistor or from the fourth level to thethird level to turn on the transistor, to regulate at a predeterminedcurrent magnitude a current that flows through at least the one or morelight emitting diodes. In certain examples, the voltage generatorincludes at least one selected from a group consisting of a junctionfield-effect transistor and a low dropout regulator. In some examples,the first level corresponds to a logic high level; and the second levelcorresponds to a logic low level.

According to some embodiments, a method for controlling one or morelight emitting diodes, the method comprising: receiving a cathodevoltage from a cathode of a diode, the diode including an anodeconfigured to receive a rectified voltage generated by a rectifyingbridge; generating a first signal based at least in part on the cathodevoltage; receiving the first signal; generating a second signal based atleast in part on the first signal; and outputting the second signal to agate terminal of a transistor, the transistor including a sourceterminal coupled to a first resistor, the transistor further including adrain terminal coupled to the one or more light emitting diodes and anoutput capacitor connected to the cathode of the diode; wherein thegenerating a first signal based at least in part on the cathode voltageincludes: if the cathode voltage has not remained higher than apredetermined voltage threshold for a time duration that is equal to orlonger than a predetermined time threshold, generating the first signalat a first level to keep the transistor turned on, the predeterminedtime threshold being larger than zero in magnitude; and if the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generating the first signal at a second level to allow thetransistor to be turned on and to be turned off, the second level beingdifferent from the first level. For example, the method is implementedaccording to at least FIG. 1 , FIG. 2 , FIG. 3 , FIG. 4 , and/or FIG. 5.

In certain examples, the predetermined time threshold is longer than atleast one cycle of the rectified voltage in duration. In some examples,the outputting the second signal to a gate terminal of a transistorincludes: if the cathode voltage has not remained higher than thepredetermined voltage threshold for the time duration that is equal toor longer than the predetermined time threshold, keep the transistorturned on to charge the output capacitor. In certain examples, thegenerating a first signal based at least in part on the cathode voltagefurther includes: determining whether the cathode voltage is higher thanthe predetermined voltage threshold; generating a third signalindicating whether the cathode voltage is higher than the predeterminedvoltage threshold; receiving the third signal; and generating a timersignal indicating whether the cathode voltage has remained higher thanthe predetermined voltage threshold for the time duration that is equalto or longer than the predetermined time threshold.

In some examples, the generating a first signal based at least in parton the cathode voltage further includes: receiving the timer signal; andgenerating the first signal based at least in part on the timer signal.In certain examples, the generating the first signal based at least inpart on the timer signal includes: if the timer signal indicates thatthe cathode voltage has not remained higher than the predeterminedvoltage threshold for the time duration that is equal to or longer thanthe predetermined time threshold, generating the first signal at thefirst level to keep the transistor turned on; and if the timer signalindicates that the cathode voltage has remained higher than thepredetermined voltage threshold for the time duration that is equal toor longer than the predetermined time threshold, generating the firstsignal at the second level to allow the transistor to be turned on andto be turned off. In some examples, the generating a second signal basedat least in part on the first signal includes: if the first signal is atthe first level, generating the second signal at a third level to turnon the transistor; and if the first signal is at the second level,changing the second signal from the third level to a fourth level toturn off the transistor or from the fourth level to the third level toturn on the transistor.

In certain examples, the transistor is an NMOS transistor; the thirdlevel corresponds to a high voltage level; and the fourth levelcorresponds to a low voltage level, the low voltage being lower than thehigh voltage level. In some examples, the generating a second signalbased at least in part on the first signal further includes: receiving afeedback signal from the first resistor; and if the first signal is atthe second level, changing, based at least in part on the feedbacksignal, the second signal from the third level to the fourth level toturn off the transistor or from the fourth level to the third level toturn on the transistor. In certain examples, the changing, based atleast in part on the feedback signal, the second signal from the thirdlevel to the fourth level to turn off the transistor or from the fourthlevel to the third level to turn on the transistor if the first signalis at the second level includes: if the first signal is at the secondlevel, changing the second signal, based at least in part on thefeedback signal, from the third level to the fourth level to turn offthe transistor or from the fourth level to the third level to turn onthe transistor, to regulate at a predetermined current magnitude acurrent that flows through at least the one or more light emittingdiodes. In some examples, the first level corresponds to a logic highlevel; and the second level corresponds to a logic low level.

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. As an example, some orall components of various embodiments of the present invention each are,individually and/or in combination with at least another component,implemented in one or more circuits, such as one or more analog circuitsand/or one or more digital circuits. For example, various embodimentsand/or examples of the present invention can be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments.

What is claimed is:
 1. A system for controlling one or more lightemitting diodes, the system comprising: a power supply controllerconfigured to receive a cathode voltage from a cathode of a diode, thediode including an anode configured to receive a rectified voltagegenerated by a rectifying bridge, the power supply controller beingfurther configured to generate a first signal based at least in part onthe cathode voltage; and a driver configured to receive the first signaland generate a second signal based at least in part on the first signal,the driver being further configured to output the second signal to agate terminal of a transistor, the transistor including a sourceterminal coupled to the driver and a first resistor, the transistorfurther including a drain terminal coupled to the one or more lightemitting diodes and an output capacitor connected to the cathode of thediode; wherein the power supply controller and the driver are furtherconfigured to: if the cathode voltage has not remained higher than apredetermined voltage threshold for a time duration that is equal to orlonger than a predetermined time threshold, generate the first signal ata first level to keep the transistor turned on, the predetermined timethreshold being larger than zero in magnitude; and if the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generate the first signal at a second level to allow thetransistor to be turned on and to be turned off, the second level beingdifferent from the first level.
 2. The system of claim 1 wherein thepredetermined time threshold is longer than at least one cycle of therectified voltage in duration.
 3. The system of claim 1 wherein thepower supply controller and the driver are further configured to, if thecathode voltage has not remained higher than the predetermined voltagethreshold for the time duration that is equal to or longer than thepredetermined time threshold, keep the transistor turned on to chargethe output capacitor.
 4. The system of claim 1 wherein the power supplycontroller includes: a voltage generator configured to receive thecathode voltage; an operation controller coupled to the voltagegenerator and configured to generate the first signal; a voltagedetector configured to receive the cathode voltage, determine whetherthe cathode voltage is higher than the predetermined voltage threshold,and generate a third signal indicating whether the cathode voltage ishigher than the predetermined voltage threshold; and a timer configuredto receive the third signal and generate a timer signal, the timersignal indicating whether the cathode voltage has remained higher thanthe predetermined voltage threshold for the time duration that is equalto or longer than the predetermined time threshold.
 5. The system ofclaim 4 wherein the operation controller is further configured toreceive the timer signal and generate the first signal based at least inpart on the timer signal.
 6. The system of claim 5 wherein the operationcontroller is further configured to: if the timer signal indicates thatthe cathode voltage has not remained higher than the predeterminedvoltage threshold for the time duration that is equal to or longer thanthe predetermined time threshold, generate the first signal at the firstlevel to keep the transistor turned on; and if the timer signalindicates that the cathode voltage has remained higher than thepredetermined voltage threshold for the time duration that is equal toor longer than the predetermined time threshold, generate the firstsignal at the second level to allow the transistor to be turned on andto be turned off.
 7. The system of claim 6 wherein the driver is furtherconfigured to: if the first signal is at the first level, generate thesecond signal at a third level to turn on the transistor; and if thefirst signal is at the second level, change the second signal from thethird level to a fourth level to turn off the transistor or from thefourth level to the third level to turn on the transistor.
 8. The systemof claim 7 wherein: the transistor is an NMOS transistor; the thirdlevel corresponds to a high voltage level; and the fourth levelcorresponds to a low voltage level, the low voltage being lower than thehigh voltage level.
 9. The system of claim 7 wherein the diver isfurther configured to: receive a feedback signal from the firstresistor; and if the first signal is at the second level, change, basedat least in part on the feedback signal, the second signal from thethird level to the fourth level to turn off the transistor or from thefourth level to the third level to turn on the transistor.
 10. Thesystem of claim 9 wherein the diver is further configured to: if thefirst signal is at the second level, change the second signal, based atleast in part on the feedback signal, from the third level to the fourthlevel to turn off the transistor or from the fourth level to the thirdlevel to turn on the transistor, to regulate at a predetermined currentmagnitude a current that flows through at least the one or more lightemitting diodes.
 11. The system of claim 4 wherein the voltage generatorincludes at least one selected from a group consisting of a junctionfield-effect transistor and a low dropout regulator.
 12. The system ofclaim 1 wherein: the first level corresponds to a logic high level; andthe second level corresponds to a logic low level.
 13. A method forcontrolling one or more light emitting diodes, the method comprising:receiving a cathode voltage from a cathode of a diode, the diodeincluding an anode configured to receive a rectified voltage generatedby a rectifying bridge; generating a first signal based at least in parton the cathode voltage; receiving the first signal; generating a secondsignal based at least in part on the first signal; and outputting thesecond signal to a gate terminal of a transistor, the transistorincluding a source terminal coupled to a first resistor, the transistorfurther including a drain terminal coupled to the one or more lightemitting diodes and an output capacitor connected to the cathode of thediode; wherein the generating a first signal based at least in part onthe cathode voltage includes: if the cathode voltage has not remainedhigher than a predetermined voltage threshold for a time duration thatis equal to or longer than a predetermined time threshold, generatingthe first signal at a first level to keep the transistor turned on, thepredetermined time threshold being larger than zero in magnitude; and ifthe cathode voltage has remained higher than the predetermined voltagethreshold for the time duration that is equal to or longer than thepredetermined time threshold, generating the first signal at a secondlevel to allow the transistor to be turned on and to be turned off, thesecond level being different from the first level.
 14. The method ofclaim 13 wherein the predetermined time threshold is longer than atleast one cycle of the rectified voltage in duration.
 15. The method ofclaim 13 wherein the outputting the second signal to a gate terminal ofa transistor includes: if the cathode voltage has not remained higherthan the predetermined voltage threshold for the time duration that isequal to or longer than the predetermined time threshold, keep thetransistor turned on to charge the output capacitor.
 16. The method ofclaim 13 wherein the generating a first signal based at least in part onthe cathode voltage further includes: determining whether the cathodevoltage is higher than the predetermined voltage threshold; generating athird signal indicating whether the cathode voltage is higher than thepredetermined voltage threshold; receiving the third signal; andgenerating a timer signal indicating whether the cathode voltage hasremained higher than the predetermined voltage threshold for the timeduration that is equal to or longer than the predetermined timethreshold.
 17. The method of claim 16 wherein the generating a firstsignal based at least in part on the cathode voltage further includes:receiving the timer signal; and generating the first signal based atleast in part on the timer signal.
 18. The method of claim 17 whereinthe generating the first signal based at least in part on the timersignal includes: if the timer signal indicates that the cathode voltagehas not remained higher than the predetermined voltage threshold for thetime duration that is equal to or longer than the predetermined timethreshold, generating the first signal at the first level to keep thetransistor turned on; and if the timer signal indicates that the cathodevoltage has remained higher than the predetermined voltage threshold forthe time duration that is equal to or longer than the predetermined timethreshold, generating the first signal at the second level to allow thetransistor to be turned on and to be turned off.
 19. The method of claim18 wherein the generating a second signal based at least in part on thefirst signal includes: if the first signal is at the first level,generating the second signal at a third level to turn on the transistor;and if the first signal is at the second level, changing the secondsignal from the third level to a fourth level to turn off the transistoror from the fourth level to the third level to turn on the transistor.20. The method of claim 19 wherein: the transistor is an NMOStransistor; the third level corresponds to a high voltage level; and thefourth level corresponds to a low voltage level, the low voltage beinglower than the high voltage level.
 21. The method of claim 19 whereinthe generating a second signal based at least in part on the firstsignal further includes: receiving a feedback signal from the firstresistor; and if the first signal is at the second level, changing,based at least in part on the feedback signal, the second signal fromthe third level to the fourth level to turn off the transistor or fromthe fourth level to the third level to turn on the transistor.
 22. Themethod of claim 21 wherein the changing, based at least in part on thefeedback signal, the second signal from the third level to the fourthlevel to turn off the transistor or from the fourth level to the thirdlevel to turn on the transistor if the first signal is at the secondlevel includes: if the first signal is at the second level, changing thesecond signal, based at least in part on the feedback signal, from thethird level to the fourth level to turn off the transistor or from thefourth level to the third level to turn on the transistor, to regulateat a predetermined current magnitude a current that flows through atleast the one or more light emitting diodes.
 23. The method of claim 13wherein: the first level corresponds to a logic high level; and thesecond level corresponds to a logic low level.